Biology Chemistry of Life

Structure of Atoms Atoms are made up of protons (+), neutrons (0), and electrons (-). Protons and neutrons are in the nucleus of the atom. Electrons are in constant motion outside the nucleus (electron cloud). ELEMENTS are pure substances consisting of one type of atom.

C 6 Carbon 12.011 An Element in the Periodic Table Section 2-1 Go to Section:

ISOTOPES Isotopes are atoms of the same element that have a different number of neutrons. This results in the isotopes having the same atomic number, but different atomic masses. Carbon-12, Carbon-13, and Carbon-14 are isotopes. Radioactive isotopes can be used to determine the age of materials, treat cancer, and to trace the movement of substances in organisms.

Figure 2-2 Isotopes of Carbon Section 2-1 Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons 6 electrons 6 protons 8 neutrons Go to Section:

Chemical Compounds A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. The chemical formula for a compound tells the types of elements that are in it, and the ratio in which the atoms of those elements combine. Ex) H2O means two hydrogen atoms always combine with one oxygen atom to form a water molecule.

CHEMICAL BONDS Ionic bonds form when two or more electrons are transferred from one atom to another. Ex) NaCl Covalent bonds form when electrons are shared between atoms. Ex) water Van der Waals forces are slight attractions that occur between oppositely charged regions of nearby molecules. Not as strong as ionic or covalent bonds.

Figure 2-3 Ionic Bonding Sodium atom (Na) Chlorine atom (Cl) Section 2-1 Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-) Transfer of electron Protons +11 Electrons -11 Charge 0 Protons +17 Electrons -17 Charge 0 Protons +11 Electrons -10 Charge +1 Protons +17 Electrons -18 Charge -1 Go to Section:

Water, Water Everywhere If you have ever seen a photograph of Earth from space, you know that much of the planet is covered by water. Water makes life on Earth possible. If life as we know it exists on some other planet, water must be present to support that life. Go to Section:

Properties of Water Water molecules are neutral, but polar. There is a slightly negative charge on oxygen, and slightly positive charge on the hydrogen atoms. Water molecules are polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. Water is extremely cohesive because of its ability to form hydrogen bonds.

Cohesion vs. Adhesion Cohesion is the attraction between molecules of the same substance. Ex) water molecules to each other Adhesion is the attraction between molecules of different substances. Ex) water molecules cling to the inside of a plant stem

Mixtures Mixtures are materials composed of two or more elements or compounds that are physically mixed together but not chemically combined. Two types of mixtures made with water are homogenous mixtures and suspensions.

Homogenous mixtures Solution: Mixture of two or more substances in which the molecules of the substance are evenly distributed. Solvent- substance in which a solute is dissolved to form a solution. Ex) water Solute- substance dissolved in a solvent to make a solution Ex) salt

Figure 2-9 NaCI Solution Cl- Cl- Na+ Na+ Water Water Section 2-2 Go to Section:

Suspensions Mixtures of water and undissolved materials that are so small they do not settle out. Examples are blood and milk.

Acids, Bases, and pH pH measures the concentration of hydrogen ions (H+) in solution. Ranges from 0 to 14. ACIDIC solutions have high H+ concentrations, and a pH less than 7. BASIC solutions have a low concentration of H+, and a pH greater than 7.

Solutions with pH of 7, such as pure water, are NEUTRAL. BUFFERS are weak acids and bases that can react with strong acids or bases to prevent sudden changes in pH.

pH Scale Increasingly Basic Neutral Increasingly Acidic Section 2-2 Oven cleaner Bleach Ammonia solution Increasingly Basic Soap Sea water Human blood Neutral Pure water Milk Normal rainfall Acid rain Increasingly Acidic Tomato juice Lemon juice Stomach acid Go to Section:

Carbon Compounds Carbon forms strong covalent bonds. Carbon atoms can bond to other carbon atoms to form long chains. Carbon-carbon bonds can be single, double, or triple bonds. Carbon atoms can close upon themselves to from rings.

Figure 2-11 Carbon Compounds Section 2-3 Methane Acetylene Butadiene Benzene Isooctane Go to Section:

Macromolecules Macromolecules are made from thousands of smaller molecules. Monomers-small unit that can join with other small units to form polymers. Polymers-large compound formed from combinations of many monomers. Four groups of organic compounds found in living things are carbohydrates, lipids, nucleic acids, and proteins.

Carbohydrates Carbohydrates are compounds made up of carbon, hydrogen, and oxygen atoms, usually in a ratio of 1 : 2 : 1. Living things use carbohydrates as their main source of energy. Stored as glycogen in animals and starch in plants. Plants and some animals use carbohyrates for structural purposes. Plants have cellulose, animals have chitin.

Carbohydrate storage Glycogen in an animal cell Starch in a plant cell

Carbohydrates for structure Chitin in animal cells—arthropod shells and insects. Also found in cells walls of fungi Cellulose in plant cells (we don’t have enzymes to digest it)

Monosaccharides are single sugar molecules, such as glucose. Polysaccharides are large macromolecules formed from monosaccharides, such as starch.

Figure 2-13 A Starch Section 2-3 Starch Glucose Go to Section:

Lipids Lipids are a group of organic molecules made mostly of carbon and hydrogen atoms. Generally not soluble in water. Grouped as fats, oils, and waxes. Used to store energy, form parts of biological membranes, and form waterproof coverings. Examples: steroids, triglycerides

Saturated fats have the maximum number of possible hydrogen bonds Saturated fats have the maximum number of possible hydrogen bonds. Tend to be solid at room temperature. Examples: meat fat, Crisco, butter, lard, etc. Unsaturated fats have at least one carbon-carbon double bond C=C. Polyunsaturated fats contain C=C double bonds, and are liquid at room temperature, Examples: olive oil, vegetable oils

Saturated vs. Unsaturated Fats

Nucleic acids Nucleic acids are macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus Nucleotides have three parts: 5-carbon sugar, phosphate group, and a nitrogenous base. Nucleic acids store and transmit hereditary or genetic information Examples: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)

The Double Helix Nucleotide is a sugar, phosphate, & nitrogen base Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Proteins Proteins are macromolecules that contain nitrogen, carbon, hydrogen, and oxygen. Proteins are polymers of amino acids. Have an amino group (--NH2) and a carboxyl group (--COOH) at the other. The amino acids form chains that fold into complex structures.

Figure 2-16 Amino Acids General structure Alanine Serine Section 2-3 Amino group Carboxyl group General structure Alanine Serine Go to Section:

Proteins control the rate of reactions and regulate cell processes. Proteins help form muscle and bone tissue. Proteins help transport substances into and out of cells. Help fight diseases.

Figure 2-17 A Protein Section 2-3 Amino acids Go to Section:

Concept Map Carbon Compounds Carbohydrates Lipids Nucleic acids Section 2-3 Carbon Compounds include Carbohydrates Lipids Nucleic acids Proteins that consist of that consist of that consist of that consist of Sugars and starches Fats and oils Nucleotides Amino Acids which contain which contain which contain which contain Carbon, hydrogen, oxygen Carbon,hydrogen, oxygen, nitrogen, phosphorus hydrogen,oxygen, nitrogen, Go to Section:

Chemical reactions and enzymes A chemical reaction is a process that changes one set of chemicals into another set of chemicals. Chemical reactions always involve the breaking of bonds in the reactants (starting materials) and the formation of new bonds in the products (results of the reaction) When this occurs, energy is either released or absorbed. Evidence that a chemical reaction has occurred includes heat, light, or gas being given off. Products are different from the reactants.

Energy in Reactions Since chemical reactions involve changes in chemical bonds, they also involve changes in energy. Exothermic- reactions that release energy. Often occur spontaneously. Endothermic- reactions that must absorb energy to take place. The energy needed to get a reaction started is called the activation energy.

Figure 2-19 Chemical Reactions Section 2-4 Energy-Absorbing Reaction Energy-Releasing Reaction Products Activation energy Activation energy Reactants Reactants Products Go to Section:

Enzymes Enzymes are catalysts that speed up chemical reactions that take place in cells. Enzymes lower the activation energy of the reaction. Enzymes provide a site where substrates (reactants) are brought together so that the reaction can occur. This is often described as a “lock and key” mechanism. Products are released. The enzyme is not used up in the reaction.

Effect of Enzymes Reaction pathway without enzyme Activation energy Section 2-4 Reaction pathway without enzyme Activation energy without enzyme Reactants Activation energy with enzyme Reaction pathway with enzyme Products Go to Section:

Figure 2-21 Enzyme Action Enzyme (hexokinase) Substrates Products Section 2-4 Glucose Enzyme (hexokinase) Substrates ADP Products Glucose-6- phosphate ATP Products are released Active site Enzyme-substrate complex Substrates bind to enzyme Substrates are converted into products Go to Section:

Enzymes, cont. Optimal temperature and pH are needed for most enzymes to be effective. Enzymes in the human body function best near normal body temperature: 35-400 C. Below the optimum temperature, the reaction is slower or may not occur at all.

Enzymes, cont. High temperatures disrupt the chemical bonds in the enzyme and changes it shape (denaturation). This occurs when the body has a very high fever. Since denaturation is not reversible, a temperature higher than 440 C usually causes death. Proteins begin to denature at 107 F.